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Keywords:

  • autoxidation;
  • Brønsted acid catalysis;
  • C[BOND]C coupling;
  • C[BOND]H activation;
  • high-pressure chemistry;
  • oxygen

Abstract

An aerobic organocatalytic oxidative C[BOND]C bond formation reaction of benzylic C[BOND]H bonds with various C-nucleophiles is described. The coupling reaction proceeds by simply stirring the substrates under elevated partial pressure of oxygen in the presence of a sulfonic acid catalyst at room temperature. Elevation of the pressure enables the reaction of a broad scope of nucleophile substrates otherwise showing poor reactivity at ambient pressure. The benzylic C[BOND]H bonds of xanthene, acridanes, isochromane and related heterocycles could be functionalized with nucleophiles including ketones, 1,3-dicarbonyl compounds and aldehydes. Electron-rich arenes could be utilized as nucleophiles at elevated temperatures. The reactions are believed to proceed via autoxidation of the benzylic C[BOND]H bonds to the hydroperoxides and subsequent nucleophilic substitution catalyzed by sulfonic acids.